Yes. A false positive test means the test looks as if it is positive, but it is really negative. This happens more often in persons who have a low risk for the disease for which they are being tested. For example, false positive anti-HCV tests happen more often in persons such as blood donors who are at low risk for hepatitis C.

It is possible to get a false positive test result. This happens when a doctor or laboratory has not performed a confirmatory antibody test before giving people their results. When a person has an antibody test, the lab usually runs two different kinds of tests. One is called an EIA test which is highly sensitive. It can sometimes overreact, so a positive result with the EIA is usually followed up with a RIBA test which is a sophisticated, highly-specific, antibody test.

Yes. Persons with early infection may not as yet have developed antibody levels high enough that the test can measure. In addition, some persons may lack the (immune) response necessary for the test to work well. In these persons, research-based tests such as PCR may be considered.

False negative results are more common than false positives - and are primarily due to inaccuracies in timing of the test or carelessness in the test procedure itself. Please follow test instructions with circumspection and precision. A false negative result can also stem from using a diluted urine sample and/or from taking a test too early in pregnancy. First morning urine contains the most concentrated presence of hCG - which makes it the ideal sample for pregnancy testing.

Measure the level of ALT ( alanine aminotransferase, a liver enzyme) in the blood. An elevated ALT indicates inflammation of the liver and you should be checked further for chronic (long-term) liver disease and possible treatment. An Infectious Diseases professional familiar with chronic hepatitis C should do the evaluation.

A positive test result may mean that your dog has bladder cancer. However, there are conditions other than bladder cancer that can cause a positive result. A positive test result will be used in conjunction with signs, symptoms, and possibly other diagnostic tests such as ultrasound to make a definitive diagnosis for your dog.

A "false-reactive" (or "false-positive") test result means that the initial screening test was "reactive" but a more precise follow-up test was negative.

Tests are very accurate but not 100 percent accurate. Usually samples are divided so if an initial test is positive a confirmation test can be conducted. Federal guidelines are in place to ensure accuracy and fairness in drug testing programs.

A false positive hearing screening test result is when a baby does not have a hearing loss but the newborn does not pass the hearing screening. Hearing screening tests are not meant to diagnose hearing loss in infants. Instead, they are meant to find all infants that might have a hearing loss. Because they are not a diagnostic test, hearing screening tests sometimes misidentify infants as having a hearing loss.

In 2-5% of individuals who have recently received an influenza vaccination, there may be a temporary false positive EIA.

False positive tests are rare - though there are instances and conditions where they can occur. For example, some tissues in a non-pregnant woman can produce hCG, though the levels are usually so low they are not detectable by home pregnancy tests (though our tests are the most sensitive on the market). Secondly, research indicates that half of all "conceptions" (fertilized eggs) do not go forward as a developing pregnancy.

The most commonly used syphilis tests screen for an antibody to the syphilis organism. Lupus patients sometimes have a very similar antibody. This similar antibody, the antiphospholipid antibody (aPL), can cause an incorrect positive result on a syphilis test. If the doctor suspects that the patient may not really have syphilis, he may choose to then run a different, more complicated and expensive test that checks specifically for the syphilis organism.